1 //===---------- speculation.cpp - Utilities for Speculation ----------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #include "llvm/ExecutionEngine/Orc/Speculation.h" 10 #include "llvm/IR/BasicBlock.h" 11 #include "llvm/IR/Function.h" 12 #include "llvm/IR/IRBuilder.h" 13 #include "llvm/IR/Instruction.h" 14 #include "llvm/IR/Instructions.h" 15 #include "llvm/IR/LLVMContext.h" 16 #include "llvm/IR/Module.h" 17 #include "llvm/IR/Type.h" 18 #include "llvm/IR/Verifier.h" 19 20 namespace llvm { 21 22 namespace orc { 23 24 // ImplSymbolMap methods 25 void ImplSymbolMap::trackImpls(SymbolAliasMap ImplMaps, JITDylib *SrcJD) { 26 assert(SrcJD && "Tracking on Null Source .impl dylib"); 27 std::lock_guard<std::mutex> Lockit(ConcurrentAccess); 28 for (auto &I : ImplMaps) { 29 auto It = Maps.insert({I.first, {I.second.Aliasee, SrcJD}}); 30 // check rationale when independent dylibs have same symbol name? 31 assert(It.second && "ImplSymbols are already tracked for this Symbol?"); 32 (void)(It); 33 } 34 } 35 36 // Trigger Speculative Compiles. 37 void Speculator::speculateForEntryPoint(Speculator *Ptr, uint64_t StubId) { 38 assert(Ptr && " Null Address Received in orc_speculate_for "); 39 Ptr->speculateFor(ExecutorAddr(StubId)); 40 } 41 42 Error Speculator::addSpeculationRuntime(JITDylib &JD, 43 MangleAndInterner &Mangle) { 44 ExecutorSymbolDef ThisPtr(ExecutorAddr::fromPtr(this), 45 JITSymbolFlags::Exported); 46 ExecutorSymbolDef SpeculateForEntryPtr( 47 ExecutorAddr::fromPtr(&speculateForEntryPoint), JITSymbolFlags::Exported); 48 return JD.define(absoluteSymbols({ 49 {Mangle("__orc_speculator"), ThisPtr}, // Data Symbol 50 {Mangle("__orc_speculate_for"), SpeculateForEntryPtr} // Callable Symbol 51 })); 52 } 53 54 // If two modules, share the same LLVMContext, different threads must 55 // not access them concurrently without locking the associated LLVMContext 56 // this implementation follows this contract. 57 void IRSpeculationLayer::emit(std::unique_ptr<MaterializationResponsibility> R, 58 ThreadSafeModule TSM) { 59 60 assert(TSM && "Speculation Layer received Null Module ?"); 61 assert(TSM.getContext().getContext() != nullptr && 62 "Module with null LLVMContext?"); 63 64 // Instrumentation of runtime calls, lock the Module 65 TSM.withModuleDo([this, &R](Module &M) { 66 auto &MContext = M.getContext(); 67 auto SpeculatorVTy = StructType::create(MContext, "Class.Speculator"); 68 auto RuntimeCallTy = FunctionType::get( 69 Type::getVoidTy(MContext), 70 {SpeculatorVTy->getPointerTo(), Type::getInt64Ty(MContext)}, false); 71 auto RuntimeCall = 72 Function::Create(RuntimeCallTy, Function::LinkageTypes::ExternalLinkage, 73 "__orc_speculate_for", &M); 74 auto SpeclAddr = new GlobalVariable( 75 M, SpeculatorVTy, false, GlobalValue::LinkageTypes::ExternalLinkage, 76 nullptr, "__orc_speculator"); 77 78 IRBuilder<> Mutator(MContext); 79 80 // QueryAnalysis allowed to transform the IR source, one such example is 81 // Simplify CFG helps the static branch prediction heuristics! 82 for (auto &Fn : M.getFunctionList()) { 83 if (!Fn.isDeclaration()) { 84 85 auto IRNames = QueryAnalysis(Fn); 86 // Instrument and register if Query has result 87 if (IRNames) { 88 89 // Emit globals for each function. 90 auto LoadValueTy = Type::getInt8Ty(MContext); 91 auto SpeculatorGuard = new GlobalVariable( 92 M, LoadValueTy, false, GlobalValue::LinkageTypes::InternalLinkage, 93 ConstantInt::get(LoadValueTy, 0), 94 "__orc_speculate.guard.for." + Fn.getName()); 95 SpeculatorGuard->setAlignment(Align(1)); 96 SpeculatorGuard->setUnnamedAddr(GlobalValue::UnnamedAddr::Local); 97 98 BasicBlock &ProgramEntry = Fn.getEntryBlock(); 99 // Create BasicBlocks before the program's entry basicblock 100 BasicBlock *SpeculateBlock = BasicBlock::Create( 101 MContext, "__orc_speculate.block", &Fn, &ProgramEntry); 102 BasicBlock *SpeculateDecisionBlock = BasicBlock::Create( 103 MContext, "__orc_speculate.decision.block", &Fn, SpeculateBlock); 104 105 assert(SpeculateDecisionBlock == &Fn.getEntryBlock() && 106 "SpeculateDecisionBlock not updated?"); 107 Mutator.SetInsertPoint(SpeculateDecisionBlock); 108 109 auto LoadGuard = 110 Mutator.CreateLoad(LoadValueTy, SpeculatorGuard, "guard.value"); 111 // if just loaded value equal to 0,return true. 112 auto CanSpeculate = 113 Mutator.CreateICmpEQ(LoadGuard, ConstantInt::get(LoadValueTy, 0), 114 "compare.to.speculate"); 115 Mutator.CreateCondBr(CanSpeculate, SpeculateBlock, &ProgramEntry); 116 117 Mutator.SetInsertPoint(SpeculateBlock); 118 auto ImplAddrToUint = 119 Mutator.CreatePtrToInt(&Fn, Type::getInt64Ty(MContext)); 120 Mutator.CreateCall(RuntimeCallTy, RuntimeCall, 121 {SpeclAddr, ImplAddrToUint}); 122 Mutator.CreateStore(ConstantInt::get(LoadValueTy, 1), 123 SpeculatorGuard); 124 Mutator.CreateBr(&ProgramEntry); 125 126 assert(Mutator.GetInsertBlock()->getParent() == &Fn && 127 "IR builder association mismatch?"); 128 S.registerSymbols(internToJITSymbols(*IRNames), 129 &R->getTargetJITDylib()); 130 } 131 } 132 } 133 }); 134 135 assert(!TSM.withModuleDo([](const Module &M) { return verifyModule(M); }) && 136 "Speculation Instrumentation breaks IR?"); 137 138 NextLayer.emit(std::move(R), std::move(TSM)); 139 } 140 141 } // namespace orc 142 } // namespace llvm 143